
Research at the Adaptive Communications
and Signal Processing Group (ACSP) at Cornell
University focuses on three major areas:
Adaptive techniques for wireless networks
Wireless communication and information
theory
Adaptive signal processing
We investigate theoretical and practical issues
in wireless networks including large scale sensor networks and high performance wireless LAN.
We are interested signal processing and information theoretic aspects of the physical
layer design and the interaction between the physical layer and the medium access control
layer. Applications include future wireless systems, wireless LAN, ad hoc networking,
terrestrial HDTV broadcasting, and DSL/cable modems.
Current
projects
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Signal Processing for
Random Access: A Cross Layer Approach (NSF)
This research aims to
develop novel random access techniques for two
emerging wireless applications: high data-rate wireless LAN for hot-spot
access and information extraction in large-scale and low-power sensor
networks. For both applications, conventional medium access control that
assumes simplistic channel model is one of the major performance
bottlenecks. We explore new cross-layer design strategies by exploiting
tight interactions between signal processing at the physical layer and the
medium access control sublayer. The research has two major themes. The
first involves developing optimal medium access strategies that capitalize
the multi-packet reception capabilities of the physical layer and provide
capacity achieving random access. Signal processing techniques are
developed to maximize the stable throughput of users. Rate allocations,
quality of service requests, and pricing structures are designed based on
the characterization of the capacity and stability region of optimal
random access protocols. The second theme focuses on low power and energy
efficient random access for large-scale sensor networks. The cross-layer
design approaches take the form of utilizing channel state information at
the physical layer. Distributed, scalable random access protocols with
low complexity are investigated for the sensor reach-back problem. Novel
signal processing techniques at the sensor node and the mobile access
point are developed for energy efficient medium access.
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Channel
and QoS Adaptive Multimedia Wireless Ad-Hoc Networks (ONR)
Funded by the Department of Defense,
this Multidisciplinary University Research Initiative (MURI) focuses on
new design methodologies for wireless multimedia networks. Specific topics
include signal processing for wireless networks, protocol aided signal
processing for adaptive receivers, adaptive source and channel codings
for multimedia wireless networks, and asynchronous VLSI circuit simulation
of large scale wireless networks.
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Wireless Ad-Hoc Networks with Receiver
Multipacket Reception
Supported by the Army Research Office
(ARO), this project investigates receiver multipacket reception (MPR) in
wireless ad-hoc networks. The objective of the research is twofold. First,
a general theoretical framework is developed for the analysis of code division
multiple access (CDMA) ad-hoc networks whose nodes are capable of simultaneously
detecting multiple packets. Potential improvements due to MPR in network
throughput, delay, and stability are measured against the increased complexity
of receiver implementations. Tradeoffs among spread spectrum bandwidth,
error control, and packet error probability are examined. Second, multipacket
reception techniques are developed and analyzed for slow frequency hopping
code division multiple access (SFH-CDMA) ad hoc networks. Packet formats,
spatial and propagation diversities are exploited for signal processing
based receiver MPR techniques. Resolvability of multipacket reception techniques
is analyzed as a function of signal-to-noise ratio, multiaccess interference,
and transmission protocols.
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Adaptive Signal Processing in Asynchronous
Wireless Networks
This project is supported by the
National Science Foundation. The objective is to develop adaptive and spectrally
efficient channel equalization and estimation schemes for wireless ATM
and other asynchronous networks. Methodologies that do not rely on the
transmission of training signals will be considered. Emphasize will be
placed on the exploitation of data packet structure, medium access control
protocols and temporal and spatial diversities. This includes the possible
use of ATM cell header information, the guard-period in the multiple access
protocol, and the error correction and detection structure imbeded in the
ATM cels.
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Channel Estimation and Equalization
in Packet Radio Networks
This project is supported by the
Center for Research on Applied Signal Processing (CRASP). The thrust of
the research is transceiver designs for packet radio networks. Specifically,
we investigate blind and semi-blind channel estimation and equalization
in packet transmissions such as those employed in EDGE, GPRS, Bluetooth
and Wideband CDMA.
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Adaptive Receivers for Terrestrial
Broadcast HDTV
This project focuses on adaptive
receiver design for the next generation terrestrial broadcast HDTV. The
research includes adaptive channel estimation and equalization techniques
for broadcast channels. This research is supported by Philips.